This study is designed to understand the value of shade development in skin cancer prevention and test predictions from social ecologic models that health behavior results from the interplay among the built environment, social environment, individual factors, setting features, and perceived environment. Use of shade is recommended by health authorities worldwide;however, shade provision requires expensive physical environment changes and may be effective only when health education has created a social environment (e.g., norms) and individual factors (e.g., habits) that motivates its use. A multi-national research team will explore the use of built shade in passive recreation areas (PRAs;areas for sitting/ standing while socializing, preparing/eating a meal, watching or coaching sports, watching a concert, taking a class, or waiting, or areas where people stroll for sightseeing, while observing outdoor displays, or shopping) within public parks and compare use between the United States and Australia to prospectively test the moderating influence of social environment on the built environment. Pilot studies confirmed that adults in Melbourne, Victoria, Australia had stronger sun protection habits and norms than adults in Denver, Colorado, USA. The specific aims of the project are to: a) introduce built shade structures (i.e., shade sails) in public parks in Denver and Melbourne;b) compare the use of PRAs with and without built shade;c) compare the change in use of the PRAs in Denver and Melbourne after introduction of built shade, and d) examine the relationship among social environment, individual factors, other physical features of the environment micro-climate (i.e., setting), and perceived environment and built shade in posttest with PRA users. In this 60-month project, the research team will build shade sails at PRAs in public parks and compare use of PRAs to unshaded PRAs in a randomized pretest- posttest controlled design. PRAs will be stratified by location (80 in Denver and 80 in Melbourne) and randomized to one of 3 sample waves over 3 years. In each wave, areas will be pretested in a first summer, further stratified based on baseline use, and randomized to construction of a shade sail during the fall, winter, and spring. A park audit will describe the park, PRA and neighborhood setting. Post testing will occur the following summer. In total, 40 PRAs will be randomized to shade sail construction (20 per city) and 120 PRAs to control with no shade sails (60 per city). The primary outcome measures will be observation of the number of individuals using the PRAs and their average UV exposure (in minimal erythemal doses [MEDs]). Observers will record use of other PRAs, number of park users, social group, sun protection, gender, and age. Intercept surveys with PRA users will collect data on social environment, individual factors, and perceived environment. UV meters will measure UV levels. Data collection will occur on 4 weekdays and 4 weekend days over 16-weeks in the summer. Primary analyses will be performed on the weighted average use of PRAs and MEDs per day;analyses will be conducted on moderating and mediating factors to test theoretically-derived hypotheses. PUBLIC HEALTH RELEVANCE: Use of shade when outdoors is recommended by health authorities worldwide to reduce overall exposure to ultraviolet radiation;however, expensive physical environment changes are often required to provide shade and may be effective only when health education has created a social environment and individual factors that motivate shade use. A multi-national research team will explore the use of built shade in passive recreation areas (PRAs) within public parks and compare use of built shade between the United States and Australia. The specific aims of the project are to: a) introduce built shade structures (i.e., shade sails) in public parks in Denver and Melbourne;b) compare the use of PRAs with and without built shade;c) compare the change in use of the PRAs in Denver and Melbourne after introduction of built shade, and d) examine the relationship among social environment, individual factors, other physical features of the environment micro-climate (i.e., setting), and perceived environment and built shade in posttest with PRA users.